Previous plan was that they already plan to released Maemo6 device; but since they merge with Intel, current Maemo6 will be rebrand to MeeGo; the first instance of MeeGo is actually Maemo6.
Actually, this device is officially launch in Dec 2009, and up till Feb 2010, that's 3 months, and they have release 3 updates (1 being major), and another one the way. I think it's that's pretty fast, but to be honest, it's also because they release it too early being the OS still have many things to be improve, such as the Maps are not complete, phone function is still very basic, etc. Possibly they want to make quick appearance on the market to compete, thus they release it early while the features are still in basic stage. Since the device in more of an internet tablet, they mainly focus on the internet capabilities first since it's the main objective of the device, while enhancing others on the way.
Nonetheless, it's disappointing to hear the news and uncertain future for the N900; but at least they're not hiding it and suddenly just launch the MeeGo device; We can see that they're concern about the N900 future too. For those who haven't buy the device still can make their choice, for those already own it, I don't really see it as a problem for now as it's still a great device and many great apps available and coming. I don't even know what will the MeeGo OS look like, how will the phone look like, etc. Who knows? Maybe some will still prefer the N900 or Maemo5?
Anyway, as per previous mentioned, most important is to know what you want and device for yourself. Nobody is stopping anyone for not buying or buying any phones. But, it's a dilemma to decide to buy now or wait; that depends on whether one can wait or need a new phone now.
I truly agree with what u have written, andy. N900 still need a lot of improvement.. So its user need to be patient.. If you are not willingly to take the risk (of Nokia abandoning N900) and not patient enough waiting for the new updates.. My only advice is.. don't buy the phone yet.